If someone earns $50,000, spends $40,000, in four years they will have a year’s salary saved up. With that in the bank you have a fair margin of safety.
Most people don’t need a year to get a job, and can also reduce expenses in such a period. By doing so, you effectively buy freedom.
I’m guessing you wrote this because you are not able to have such a margin of savings. But I’m leaving this comment for the many readers who could do so, but have not arranged their lives such that they have it.
That assumes no unexpected expenditure though? Any medical emergency (and even a lot of non-emergencies) in the US (from what I've seen) would blow those savings quickly. Also car problems, child problems, storm damaging the house/apartment, any number of things can swallow those savings quickly and you're back to square one.
Though the non medical ones you mention can generally be handled by insurance. That usually is not tied to work. If you have a year’s savings you can generally afford insurance.
They’re tied to their jobs because healthcare costs so much. It’s unaffordable to pay $400+ per person per month plus up to $8k for out of pocket max which resets every calendar year ($16k for family) without having a job.
The $400 per person is for a young person. It goes up to $1,000 per month as you get into 50s/60s. So if you’re being prudent and factoring in the probability of not having income in your 50s/60s (age discrimination, disability, obviated from automation, outsourced), then you also need to save to plan to pay at least $12k a year in today’s money plus out of pocket maximum.
That's another thing - aren't most of them in at-will employment? Meaning they can be let go with almost no reason with no notice at any time. That's also going to put a dint in the savings.
Something can always go wrong, but it doesn't happen to everyone.
I can recommend the web site Mr Money Mustache[1] for some ideas along that line.